Tank with metallic bladder



0a. 8, 1968 H. I. WAXMAN 3,404,813

TANK WITH METALLIC BLADDER Filed Aug. 29. 196,6 4 Sheets-Sheet lf/f/FEZAT WIXMA/V INVENTOR.

A7 TOR/V5 Y Oct. 8, 1968 H. 1. WAXMAN 3,404,813

TANK WITH METALLIC BLADDER Filed Aug. 29, 1966 4 Sheets-Sheet 2 o 26 0 0o 27 o v O 2/ 0/ 22 z 50 52 #595597 J MxM/M/ 5/ f INVENTOR.

Oct. 8, 1968 H. I. WAXMAN TANK WITH METALLIC BLADDER 4 Sheets-Sheet 5Filed Aug. 29, 1966 m W/ JQ i omooo oooooooo ror ofi 7 M25597 Z MXMAWINVENTOR.

B Y F M A TTO/QA/E Y" Oct; 8, 1968 H. l. wAxMAN TANK WITH METALLICBLADDER 4 Sheets-Sheet 4 Filed Aug. 29, 1966 INVENTOR.

United States Patent 3,404,813 TANK WITH METALLIC BLADDER Herbert I.Waxman, Northridge, Califi, assignor to The Marquardt Corporation, VanNuys, Calitl, a corporation of California Filed Aug. 29, 1966, Ser. No.575,676 2 Claims. (Cl. ZZZ-386.5)

ABSTRACT OF THE DISCLOSURE The tank has a bladder made of a thin,metallic, cor- :rosive resistant material which surrounds three equallyspaced ribs located along peri-metrical lines of the tank and around acentral standpipe. The central standpipe runs the full length of thebladder and the ends of the ribs are attached at opposite ends of thestandpipe. The tank surrounds the bladder and is spaced therefrom toprovide a space which can be pressurized to collapse the bladder betweenthe ribs and thereby discharge fluid from the bladder through openingsin the ribs and in the standpipe.

This invention relates to a tank with a metallic bladder and method ofconstructing same and, more particularly, to a tank and bladder assemblyin which a liquid can be enclosed for long periods of time withoutdeterioration of the bladder or tank.

In some cases, it is desirable to fill a tank with liquid some timeprior to the installation of the tank at its point of use. This isparticularly desirable for propellant and oxidant tanks used in missilesand aircraft. After installation, it is important to have a simple meansby which the tank can be substantially emptied if this cannot beaccomplished by gravity flow. Rubber and plastic line-rs have beenutilized in tanks and the application of pressure to the exterior of theliner forces the liquid substance out of the tank. However, since suchliner materials are deteriorated by corrosive liquid substances, such ascorrosive propellants, the liners cannot be utilized to store suchsubstances for any substantial period of time.

In the present invention, a very thin metallic bladder of a corrosionresistant steel is surrounded by a steel tank which takes the mainstructural load. The frame for the bladder comprises a plurality of ribswhich are located on perimetrical lines of the tank and in differentaxial planes spaced around a central standpipe. The central standpiperuns the full length of the bladder and the ends of the ribs areattached at opposite ends of the standpipe. When fluid pressure isintroduced between the bladder and the tank, the bladder is collapsedabout the ribs and the liquid is forced out through the standpipe.Preferably, three ribs are spaced on perimetrical lines 120 apart aboutthe central standpipe so that the bladder surface between the ribspermits the bladder surface to collapse substantially into the axialplanes of the ribs.

An aluminum alloy ring is located at the longitudinal center of thestandpipe and is supported by all of the ribs. The bladder is formed intwo sections and the sections are placed over the frame from oppositeends and into edge abutment opposite the aluminum ring. Thereafter, thehalves are welded together at their edges and the aluminum ring isetched out of the interior of the bladder. Thus, the aluminum ringprovides a fixture for positioning the bladder sections for the buttwelding and for chilling the sections at the weld.

The outer tank has the same shape as the bladder and is formed of twosections which are placed around the bladder and welded together. Thetank and bladder can 7 3,404,813 Patented Oct. 8, 1968 be formed in avariety of shapes, such as spherical or cylindrical, and can beconstructed from a variety of corrosion resistant materials.

It is therefore an object of the present invention to provide a tankwith metallic bladder in which corrosive liquid substances can betotally enclosed and stored for long periods of time.

Another object of the invention is to provide a tank with metallicbladder in which the bladder is supported by an interior frameconsisting of a central standpipe and a plurality of ribs located alongthe perimeter of the bladder so that the liquid Within the tank can beexpelled by collapsing the bladder between the ribs.

Another object of the invention is to provide a method of constructing atank with metallic bladder comprising the steps of forming the bladderaround an internal frame having a removable, back-up ring centrallylocated to serve as a support and chilling member during the welding ofthe bladder sections and thereafter removing said ring.

A further object of the invention is to provide a tank and metallicbladder in which the bladder is first assembled and the outer tank thenassembled around the bladder so that the outer surface of the bladdercan be pressurized to collapse the bladder and discharge the liquidcontained therein.

Another object of the invention is to provide a tank with metallicbladder in which the bladder is supported by three ribs located alongperimeter lines of the bladder and equally spaced apart.

These and other objects of the invention not specifically set forthabove will become readily apparent from the accompanying description anddrawings in which:

FIGURE 1 is an end elevational view of the bladder frame showing thespaced ribs and the back-up ring;

FIGURE 2 is a side elevational view along line 22 of FIGURE 1 showingthe central standpipe to which the ribs are connected;

FIGURE 3 is a horizontal section along line 33 of FIGURE 2;

FIGURE 4 is a sectional view along line 44 of FIG- URE 3 showing thebladder sections welded together opposite the back-up ring;

FIGURE 5 is a side elevational view of the tank in which the bladder islocated;

FIGURE 6 is a vertical section similar to FIGURE 4 through the tankshowing the bladder supported by the internal frame and surrounded bythe tank;

FIGURE 7 is a vertical section along line 7-7 of FIGURE 6 showing theliquid conduit connected with th bladder;

FIGURE 8 is a horizontal section along line 8-8 of FIGURE 6;

FIGURE 9 is a vertical section along line 99 of FIG- URE 6 showing thepassages through which the pressurized fluid is introduced to the spacebetween the bladder and the tank;

FIGURE 10 is a section similar to FIGURE 8 showing the bladder collapsedbetween the ribs;

FIGURE 11 is a vertical section along line 11-11 of FIGURE 10 showingthe collapsed bladder; and

FIGURE 12 is a sectional view of a modified tank having a substantiallycylindrical shape.

Referring to FIGURES 1-3, the interior bladder frame assembly 20comprises a central standpipe 21 and three ribs 22, 23 and 24. Each ofthe ribs consist of a semicircular tube having openings 19 along itslength and having its ends rigidly connected to opposite ends of thestandpipe 21. A back-up ring 25 is located at the central, transverseplane of the standpipe 21 and has openings adjacent its outer peripheryfor receiving the three ribs 22- 24. Bladder 25 is fabricated of twosections 27 and 28, each of which is a half-spherical shell, and whenthe shells are placed over the ribs, they meet at the line 29 which islocated opposite the ring 25. During the welding operation, the ringserves as an assembly fixture for holding the shells in place and alsoserves to chill the material at the weld so that a suitable butt weldcan be accomplished between the edges at line 29. The ring 25 ispreferably fabricated from an aluminum alloy which can be etched outwith a caustic solution after the weld is completed. The caustic etchingsolution can be inserted through the standpipe into the bladder for thispurpose and the bladder is cleaned inside and out after the etching iscompleted. After completion of the bladder assembly illustrated inFIGURE 4 and the removal of the ring 25, the tank 30 is placed aroundthe bladder 26 and consists of two sections 31 and 32 which are buttwelded at the line 33. The tank material is considerably thicker thanthe bladder material since the tank resists the internal and externalforces and protects the bladder.

Referring to FIGURE 7, one end of the standpipe 21 comprises a liquidconduit fitting 35 connecting with the interior of the bladder. A flange36 on the fitting is welded to the edge of a circular opening 37 inbladder section 28, and end 38 of the fitting projects to the exteriorof the bladder. The other end 39 of the fitting is welded at line 40 tothe cylindrical portion 41 of the standpipe 21 which contains openings34. A passage 42 extends through fitting 35 and contains a plurality ofangular openings 43 and a plurality of radial openings 44 which lead tothe interior space 45 of the bladder. Also, the end of each rib issecured in a radial passage 46 in the fitting. An enlarged flange 50 onend 38 is secured by welding to the edge of opening 51 in the tanksection 32 of tank 30. Since both the tank and the bladder are rigidlyconnected to the fitting 35, no relative movement of these members atthis point will result. The tank section 32 carries a mounting flange 52for rigidly supporting both the tank and the bladder. Fluid to be storedis introduced through the passage 42 and enters the bladder space 45through the passages 43, 44 and 46. After the bladder is filled, thepassage 42 can be closed by any suitable closure means, such as a valve(not shown).

Referring to FIGURE 9, the other end of the standpipe 21 comprises afitting which has a flange 61 welded to the edge 62 of a circularopening in bladder section 27. Cap end 63 of fitting 60 projects into acavity 64 in the enlarged portion 65 of the tank section 31. The cavity64 serves as a guide for the cap 63 so that the bladder can moverelative to the tank while maintaining axial alignment with the tank.The enlarged portion 65 contains a passage 66 which connects with aplurality of branch passages 67 leading to the space 68 between thebladder and the tank. Also, the enlarged portion carries a flange 69which, along with the flange 52, serves to provide a support for theouter tank 30.

After assembly of the complete tank, the tank can be filled with liquidthrough the liquid conduit 42 and the liquid can be stored in the tankfor long periods of time since the metallic bladder will resist anycorrosive action of the liquid. Preferably, the bladder and tank areconstructed of CRES 321 stainless steel alloy to assure long termcompatability with the liquid. The thin shell is maintained in itsspherical configuration since it is supported at three separatelocations by the ribs. When it is desired to expel the liquid from thetank, a pressurized fluid is introduced into space 68 through passages66 and 67. Under the influence of this pressure, the bladder materialwill collapse inwardly towards the standpipe 21 in order to expel theliquid through the openings 19 in the ribs and openings 34 in thestandpipe, all connecting with passage 42 which is opened to empty thebladder. Prior to collapse, the bladder has a 3-lobe configuration witheach lobe surface being located between two ribs. When the bladder iscollapsed inwardly, each lobe forms sides 72 and 73 lying closelyadjacent to the axial plane of adjacent ribs. Therefore, the volumewithin the bladder is reduced to a very small value.

Referring to FIGURE 8, the are between a pair of ribs is 21rR/3 and thedistance between the standpipe at the lobe surface is designated as R.Thus, suflicient bladder surface is available to expel all the storedliquid since the arc length 21rR/3 of the lobe is virtually equal to itscollapsed length, namely 2R. The openings 19 in the ribs assureexpulsion from all areas of the bladder and prevent local fluidentrapment so that expulsion efficiencies of over 98% can be obtained ina single cycle operation without developing holes or tears in thebladder material. The fully collapsed bladder is illustrated in FIGURES10 and 11 and it is apparent that the bladder will bend inwardly to thecollapsible position without substantial crinkling except in thedirection of the longitudinal axis of the standpipe 21. In this axialdirection, there is about 30% excess of material as illustrated inFIGURE 11 which pleats very rapidly without any difliculty.

FIGURE 12 illustrates a modified tank which is substantially cylindricalin shape and primed numerals designate parts corresponding to those ofthe prior embodiment. It is understood that the same standpipe fittingscan be utilized although the ribs, bladder and tank have a differentshape. The cylindrical configuration has the advantage that there ismuch less material along the longitudinal axis of the standpipe whichmust be pleated.

The present invention provides a single cycle expulsion system whichoperates under a positive external expelling pressure and the thinmetallic bladder material is supported by an internal rigid frame whichprevents the inward collapse of the bladder in the absence of anexpelling pressure. The bladder collapses in the tri-lobe configurationand propellant is expelled through the central standpipe which runs thefull length of the pipe. The sections of the bladder and tank can beproduced by shear forming or other suitable process which develops highstrength in the material permitting the wall thickness to be minimized.Because of the very thin walls of the bladder, only a small differentialpressure against the bladder is required to collapse the bladder andonly a small amount of pressurized fiuid is required since the clearancespace 68 is very small. It is understood that the shape of the tank andthe number of ribs can be varied and that various means can be utilizedfor connecting the bladder and tank together and for mounting the tank.Also, various means can be used to conduct the stored liquid and thepressurized fluid. Various other modifications are contemplated by thoseskilled in the art without departing from the spirit and scope of theinvention as hereinafter defined by the appended claims.

What is claimed is:

1. A tank for storing substances such as corrosive liquids comprising:

a frame assembly comprising three equally spaced ribs located alongperimetrical lines of the tank about an .axis of said tank;

a bladder comprising a thin metal shell closely surrounding said ribs;

said tank comprising a wall of considerably greater strength than saidshell placed around said bladder and spaced therefrom to provide apressurizing space between said bladder and said tank;

liquid conduit means for introducing a liquid to be stored into saidbladder;

means for introducing a pressurized fluid into said space in order tocollapse the portions of said bladder between said ribs and dischargesaid liquid; and

said bladder and said tank being cylindrical in cross section in a planetransverse to said axis so that each of said portions of said bladderover at least a part of the axial length thereof has a circumferentiallength between ribs substantially equal to the length of said portionwhen collapsed substantially into the References Cited Planes of theribs- UNITED TAT PATENTS 2. A tank as defined in claim 1 having: S ES acentral standpipe extending longitudinally along said 3097766 7/1963Biehl et a1 222 386'5 X axis through said bladder and connected to saidribs 5 3,104,526 9/1963 Hlrschfeld et 222 386'5 X at its opposite ends;and 3,176,882 4/1965 Meermans 222394 X means for rigidly connecting saidbladder and said FOREIGN PATENTS tank to one end of said standpipe andmeans for 755,624 8/1956 Great Britain slidably connecting said bladderand said tank at the other end of said standpipe. 10 STANLEY H.TOLLBERG, Primary Examiner.

